Temperature and power supply compensation circuit for integrated circuits

• US 4,879,505 A
• Filed: 05/02/1988
• Issued: 11/07/1989
• Est. Priority Date: 12/23/1986
• Status: Expired due to Term

• Current Assignee: Analog Devices, Inc.
• Original Assignee: Analog Devices, Inc.
• Inventors: Barrow, Jeffrey G., Brokaw, Adrian P.
• Primary Examiner(s): Shoop, Jr., William W.
• Assistant Examiner(s): Hoff, Marc S.
• Application Number:
  US07/189,284
• Time in Patent Office: 554 Days
• Field of Search: 323/312, 323/907, 307/296 R, 307/310
• US Class Current: 323/312
• CPC Class Codes: G04F 1/005 using electronic timing, e.g. counting means pulse time delay arrangements H03K5/13; modifications of electronic switches for introducing a time delay before switching H03K17/28
• CPC Class Codes: G05F 1/567 for temperature compensation
• CPC Class Codes: G05F 3/225 producing a current or voltage as a predetermined function of the temperature
• CPC Class Codes: G05F 3/227 producing a current or voltage as a predetermined function of the supply voltage
• CPC Class Codes: H03K 2005/00163 using bipolar transistors
• CPC Class Codes: H03K 2005/00182 using constant current sources
• CPC Class Codes: H03K 4/50 in which a sawtooth voltage is produced across a capacitor
• CPC Class Codes: H03K 5/131 Digitally controlled
• CPC Class Codes: H03M 1/745 with weighted currents
• CPC Class Codes: Y10S 323/907 Temperature compensation of semiconductor

Abstract

A monolithic integrated circuit generates a programmable time delay under control of a digital work. The delay is generated by comparing a ramp signal to a threshold determined by the value of the digital word and appears as a time difference between a trigger pulse and a pulse generated when the value of the ramp voltage equals the value of the threshold voltage. The ramp voltage is generated by a simple resistance/capacitance charging circuit whose time constant can be adjusted by the user. The threshold voltage is set by a digital-to-analog converter (DAC) and resistor circuit which converts the digital control word into a variable voltage. In order to stabilize the device against changes in temperature and power supply variations, a voltage coupling circuit forces the threshold voltage to track changes in the ramp voltage caused by temperature and power supply variations. The coupling circuit obviates the need for percision voltage sources or current mirrors conventionally used to compensate for temperature and power supply changes. Without the need for the latter device, the integrated circuit can be easily and inexpensively fabricated of transistors of a single bipolar type.

Claims

1. In an electronic circuit having a monolithic integrated circuit with at least one integrated resistor with a first temperature coefficient and having a resistor external to said integrated circuit with a second temperature coefficient different from said first temperature coefficient, the improvement comprising an integrated bias circuit for deriving a current from said external resistor which current is compensated for temperature-induced changes in the value of said integrated resistor, said bias circuit comprising

means for passing a current which varies with said temperature-induced changes in the value of said integrated resistor through said integrated resistor to develop a voltage which is independent of said temperature induced changes in the value of said integrated resistor,

means for sensing said voltage developed across said integrated resistor, and

means for producing a voltage across said external resistor which is proportional to said voltage developed across said integrated resistor.

2. In an electronic circuit, the improvement according to claim 1, wherein the ratio of the voltage across said integrated resistor to the voltage across said external resistor is independent of temperature-induced variations in said integrated circuit.

3. In an electronic circuit, the improvement according to claim 2, wherein the magnitude of said voltage across said integrated resistor is equal to the magnitude of the voltage across said external resistor.

4. In an electronic circuit, the improvement according to claim 1, wherein said integrated resistor and said external resistor are both connected to a power supply output so that the voltage across said integrated resistor and the voltage across said external resistor are both dependent on variations in said power supply output.

5. In an electronic circuit, the improvement according to claim 4, wherein the dependence of the voltage across said integrated resistor and the voltage across said external resistor on variations in said power supply output are equal so that the voltage developed across said external resistor is not dependent on variations in said power supply output.

6. In an electronic circuit, the improvement according to claim 1, wherein said producing means comprises a first transistor and a second transistor, each having emitter, base and collection leads, the base of said first transistor being coupled to the collector of said second transistor and the base of said second transistor being coupled to the collector of said first transistor.

7. In an electronic circuit, the improvement according to claim 6, wherein the base of said first transistor is connected through a third emitter-follower transistor to the collector of said second transistor and the base of said second transistor is connected through a fourth emitter-follower transistor to the collector of said first transistor.

8. In an electronic circuit, the improvement according to claim 6, further including a power supply having an output and wherein said integrated resistor is connected between said emitter of said first transistor and said power supply output and said external resistor is connected between said emitter of said second transistor and said output of said power supply.

9. In an electronic circuit having a monolithic integrated circuit with at least one integrated resistor with a first temperature coefficient and having a resistor external to said integrated circuit with a second temperature coefficient different from said first temperature coefficient, the improvement comprising an integrated bias circuit for deriving a current from said external resistor which current is compensated for temperature-induced changes in the value of said integrated resistor, said bias circuit comprising

means for passing a current through said integrated resistor to develop a voltage,

means for sensing said voltage developed across said integrated resistor, and

means for producing a voltage across said external resistor which is proportional to said voltage developed across said integrated resistor wherein said producing means comprises a first transistor and a second transistor, each having base and collector leads, the base of said first transistor being coupled to the collector of said second transistor and the base of said second transistor being coupled to the collector of said first transistor.

10. In an electronic circuit, the improvement according to claim 9, wherein the magnitude of said voltage across said integrated resistor is equal to the magnitude of the voltage across said external resistor.

11. In an electronic circuit, the improvement according to claim 10, wherein the voltage across said integrated resistor is equal to the voltage across said external resistor independently of temperature-induced variations in said integrated circuit.

12. In an electronic circuit, the improvement according to claim 11, wherein said integrated resistor and said external resistor are both connected to a power supply output so that the voltage across said integrated resistor and the voltage across said external resistor are both dependent on variations in said power supply output.

13. In an electronic circuit, the improvement according to claim 12, wherein the dependence of the voltage across said integrated resistor and the voltage across said external resistor on variations in said power supply output are equal such that the voltage developed across said external resistor is not dependent on variations in said power supply output.

14. In an electronic circuit, the improvement according to claim 9, wherein said producing means further comprises a third transistor and a fourth transistor, said third transistor being connected in series with said first transistor and said fourth transistor being connected in series with said second transistor, the base terminals of said third and fourth transistors being connected together.

15. In an electronic circuit, the improvement according to claim 14, wherein said producing means further comprises a fifth transistor and a sixth transistor, each of said fifth and sixth transistors having a collector, a base and an emitter, said fifth and sixth transistors having their collectors coupled together, and wherein said fifth transistor is coupled between said first and second transistors such that said base of said fifth transistor is coupled to said collector of said first transistor and said emitter of said fifth transistor is coupled to said base of said second transistor, and said sixth transistor is coupled between said first and second transistors such that said emitter of said sixth transistor is coupled to said base of said first transistor and said base of said sixth transistor is coupled to said collector of said second transistor.

16. A monolithic integrated electronic circuit for deriving a current which is compensated for temperature-induced changes in said integrated circuit from a resistor having a first temperature coefficient, said integrated circuit comprising:

at least one integrated resistor with a second temperature coefficient different from said first temperature coefficient,

means for passing a current through said integrated resistor to develop a voltage,

means for sensing said voltage developed across said integrated resistor, and

means for producing a voltage across said external resistor which is proportional to said voltage developed across said integrated resistor wherein said producing means comprises a first transistor and a second transistor, each having base and collector leads, the base of said first transistor being coupled to the collector of said second transistor and the base of said second transistor being coupled to the collector of said first transistor.